1. Field of the Invention
This invention relates to a fuel injection valve, and especially to a fuel injection valve for an internal combustion engine of an automobile.
2. Description of Prior Art
A 2 cycle engine has been developed to provide a small, high power, low fuel consumption, low vibration engine. A fuel injection valve for 2 cycle engine, however, has not fully satisfied with the requirements. More often, a fuel injection valve for 4 cycle engine is modified for 2 cycle engine.
FIG. 3 is a sectional view of a conventional fuel injection valve shown in Japanese Patent Laid-Open 62 (1987)-93481. Referring to FIG. 3, fuel is provided from a fuel tank 35 to an injector 30 through a pump 36. A pressured air provided by an air source 37 is applied to a chamber 32. A figured amount of fuel is applied to a chamber 32 by the injector 30. A solenoid 31 operates a valve 33 to inject fuel with the pressured air through an injection port 34.
The above mentioned conventional fuel injection valve has two solenoids. One solenoid (not shown in FIG. 3) controls the injector 30 to supply a certain amount of fuel into the pressured chamber 32 and the other solenoid 31 controls the injection of fuel through the injection port 34. Therefore, the size of the fuel injection valve becomes big. Also it is fairly complex to control two solenoid valves with the engine operation.
An object of the present invention is to provide a fuel injection valve having improved the above-mentioned drawbacks, especially a fuel injection valve which has one solenoid.
Other objects will be apparent from an understanding the invention.
In accordance with this invention, a fuel injection valve comprises an armature made of magnetic material and having a hole, a coil placed around the armature, a fuel supply port connected to the hole of the armature, the first rod placed in said hole of the armature, a core made of magnetic material and having a hole, a control valve connected to the first rod and placed in the hole of the core, a nozzle connected to the core having an injection port, a second rod placed in the nozzle and having a fuel passage which is opened and closed by the control valve, a diaphragm attached to the second rod and dividing a room between the core and the nozzle into a fuel chamber and a mixture chamber, a first spring between the nozzle and the diaphragm to push the diaphragm toward the control valve, the second spring between the first rod and the armature to push the first rod toward the control valve, a mixture passage in the nozzle connecting the mixture chamber and the fuel passage, and a one way valve placed at the injection port of the nozzle, wherein, when the control valve closes the fuel passage of the second rod, a gap is made between the control valve and the armature to establish a passage to supply fuel into the fuel chamber from the fuel supply port.
In accordance with this invention, when a lower current power is supplied to the coil, the control valve is moved toward the armature against the second spring to open the fuel passage in the second rod. The fuel in the fuel chamber is supplied to the mixture passage and the mixture chamber through the fuel passage.
When a higher current power is supplied to the coil, the armature moves toward the core and pushes the control valve through the first rod against the first spring. The second rod is moved to open the one way valve to inject the mixture of fuel through the injection port of the nozzle.
Thus the fuel injection valve of this invention comprises one solenoid. This makes the fuel injection valve smaller. In addition to this, the diaphragm isolates the fuel chamber and the mixture chamber to prevent the mixture fuel from going back to the fuel chamber. This makes the control of fuel amount easier.